Tag Archives: knee

Knee arthritis has doubled since 1950, and we don’t really know why

Aging and obesity alone cannot explain it.


Arthritis is an inflammation of the joints (or another area where the bones come together). It’s often a chronic condition which typically starts off in the hands or feet, and most often ends up affecting the knees. It’s estimated that one in five Americans over 45 suffer from knee arthritis, and similar figures are reported in many parts of the world.

Initially, this was thought to be a consequence of aging — people lived to older ages, and therefore started suffering more from “old age diseases.” Obesity is also thought to play a role — the more you weigh, the more pressure you put on your joints. But a new study found that these factors alone cannot explain the rise in knee arthritis prevalence.

Stretching my knees

Image credits: BruceBlaus.

Ian Wallace is a paleoanthropologist at Harvard University who studies how human health and diseases have changed over time. He was aware that knee arthritis is often associated with obesity and aging, but wanted to see how these and other factors affected the prevalence of obesity through the years. So he and his colleagues studied several thousand American skeletons, from pre-industrial, early industrial, and post-industrial periods. They were specifically looking at the wear and tear in the skeleton’s knees. The age and body mass index were also assessed and through statistical processing, the impact of obesity and age was removed.

Wallace and colleagues found that 18 percent of the skeletons from the post-industrial ages (1950) had signs of advanced arthritis, compared to six and eight percent of the early industrial and prehistoric bones, respectively. The statistical model showed that neither aging nor obesity can explain the phenomenon.

“It points to this mysterious conclusion: A lot of cases of osteoarthritis, which we thought might be inevitable, may be preventable… and are due to unknown factors,” Wallace says.

Of course, both obesity and aging take their toll — no one’s saying they just don’t matter. But what this study shows is that there’s something else we’re missing.

What could it be?

The study didn’t attempt to explain the findings, but it’s not very difficult to speculate. Wallace too says that lack of physical activity is a very likely culprit. Since the 1950s, office jobs have multiplied dramatically, more and more cars flood the streets, and physical activity has declined accordingly. Sitting down is also a possible culprit. David Felson, study co-author, a renowned arthritis expert and physician at Boston University comments:

“Our joints don’t do well when they aren’t active much of the time,” Felson says.

But that might not tell the whole story. Inflammation might also be at blame. Arthritis itself is an inflammation, but different inflammations, while a natural reaction, promote injury and prevent proper healing. Francis Berenbaum, a researcher and physician at Pierre and Marie Curie University and  AP-HP hospital in Paris, France, who wasn’t involved in the study, believes an unhealthy diet might also be at blame. The same diet (high in processed foods and sugars) that’s favoring diabetes and heart diseases might also be contributing to arthritis. Other factors, such as walking more on hard surfaces such as concrete or asphalt or concrete might also contribute, but at the moment, the truth is we don’t really know.

“I study this, and I don’t know… what [more] can be done to prevent it,” Felson adds.

For now, your best bet is to keep a healthy diet and be physically active.

Journal Reference: Ian J. Wallace, Steven Worthington, David T. Felson, Robert D. Jurmain, Kimberly T. Wren, Heli Maijanen, Robert J. Woods, and Daniel E. Lieberman — Knee osteoarthritis has doubled in prevalence since the mid-20th century. doi: 10.1073/pnas.1703856114

The anterolateral ligament (ALL). (c) University of Leuven

New ligament discovered in the human knee

The human body is a complex biological entity in seemingly perfect harmony as thousands of components play their part in tandem. Discovering, describing and understanding how each of this body parts function and work together is the primary role of human anatomy. Some of you might be surprised to find that human anatomy is yet from being exhaustively described, as new body parts are discovered ever so often. For instance, doctors at University of Leuven, Belgium recently report they’ve discovered a new ligament in the human knee. Moreover, its function has also been revealed.

The anterolateral ligament (ALL). (c) University of Leuven

The anterolateral ligament (ALL). (c) University of Leuven

Termed the anterolateral ligament (ALL), and located in the human knee, the ligament’s existence was first proposed in 1879 by a French surgeon but couldn’t be proven until recently. Deep anatomy studies are made on cadavers, and death has the nasty habit of spoiling bodies and making observation difficult especially of subtle body parts. The researchers led by  Dr. Steven Claes, an orthopedic surgeon and study co-author at the University of Leuven, Belgium performed an in-depth analysis of 41 cadaver knees and found the ligament in 40 of the bodies.

“The anatomy we describe is the first precise characterization with pictures and so on, and differs in crucial points from the rather vague descriptions from the past,” Claes said. “The uniqueness about our work is not only the fact that we identified this enigmatic structure for once and for all, but we are also the first to identify its function.”

So what’s the ALL good for? One common injury to the knee is related to another ligament, the anterior cruciate ligament (ACL), which causes what’s known as a “pivot shift”. Basically, do the intense stress your knee stays in position while the rest of the leg moved, causing severe complications least not to mention excruciating pain.  The study suggests that one type pivot shift might actually caused by injury to the ALL, which helps to control the rotation of the tibia, one of the two bones in the lower leg, Claes said.

Like I said earlier, new body parts are discovered fairly often. In June scientists found a new eye layer, named Dua’s layer after its discoverer, that sits at the back of the cornea.